Technical Field
Embodiments disclosed herein are related to ophthalmic surgical microscopes. More specifically, embodiments described herein relate to an increased depth of field microscope including a movable optical element.
Related Art
Doctors can use surgical microscopes during ophthalmic surgical procedures to see fine details of a patient's eye. A successful procedure can depend on the doctor's ability to view the patient's eye clearly using the microscope. One measure of the doctor's ability to view the patient's eye is the depth of field of the microscope. The depth of field can describe an extent of a microscope subject perceivable by an observer to be in focus at the same time along a direction of the optical pathway of light reflected from the subject. For example, the depth of field can describe the longitudinal extent of a patient's eye that is in focus at the same time for a doctor along the longitudinal axis or z-axis of the microscope. A larger depth of field provides better spatial awareness to the doctor during a surgical procedure because more of the patient's eye is in focus at the same time.
Some conventional methods for increasing depth of field include implementing a larger objective lens in the microscope. Large objective lenses, however, can be costly and add unwanted bulk to the microscope. Diaphragm apertures can also be implemented, which allow for the microscope to have a smaller aperture to increase the depth of field. However, a smaller aperture reduces the photon flux or amount of light passing through the microscope optics. Conventional methods for increasing depth of field have thus been unsatisfactory.
The critical flicker fusion (CFF) rate is a quantity in psychophysics describing the frequency beyond which flicker or individual images in a successive image set are no longer independently perceivable by an observer. Above the CFF rate, the observer's brain integrates or fuses the individual images into a single image. The CFF rate has been utilized in display technology for line sequential stereo, field sequential stereo, line sequential color, field sequential color, etc. For example, in a field sequential color system, an entirely red frame, an entirely green frame, and an entirely blue frame are successively provided to the observer above the CFF rate. The observer's brain fuses the single-color frames so that the observer perceives a color image as opposed to the individual frames. Conventional microscopes do not utilize the CFF rate.